Expeditious development of integrated circuit technologies is increasingly demanding on a surface quality of a substrate material in use. With the diminishing of device dimension and reduction of focal depth of optical lithographic devices, it is required that an acceptable resolution flatness of a wafer surface should reach a nanometer order. In order to solve this problem, the CMP (Chemical Mechanical Polishing) technology that can achieve global planarization has become one of key technologies for semiconductor manufacturing. α-aluminum oxide (α-Al2O3) is substantively the same substance or material as sapphire, because their atomic arrangement patterns in the material structure are completely identical, except for the difference in polycrystal and monocrystal. Therefore, in terms of hardness, the nanometer-powder of the α-Al2O3 is equivalent to that of the sapphire crystal; therefore, it may be used for polishing the sapphire crystal. The α-Al2O3 powder may be manufactured into different polishing solutions with an average particle size ranging from 100 nm to 1000 nm above, for being used in different procedures of roughly polishing and finely polishing the sapphire crystal. However, till now, the α-Al2O3 polishing solution has not been widely applied to polishing sapphire. The α-Al2O3 particles need to be sintered at a high-temperature of 1000° C. above, causing a phase shift from a transitional aluminum oxide to α-Al2O3. During this procedure, the Al2O3 particles are easily agglomerated; besides, these agglomerates are hard and dense; therefore, they can hardly be dispersed in the polishing solution; in addition, agglomerated aluminum oxide particles very easily cause scratches and damages during the polishing procedures. Furthermore, it is also very easy for the aluminum oxide to deposit in the polishing solution to form hard chunks at the bottom of a container; therefore, it is needed to constantly stir during the use process. These drawbacks seriously hamper the aluminum oxide polishing solution to be applied for finely polishing sapphire. Moreover, in order to reduce erosion from the polishing solution to a machine stand, alkaline polishing solutions are mostly used in the market; it is also so for the aluminum oxide. The alkalinity of alkaline aluminum oxide used in the industry is generally very high, reaching 12.5 above, which also causes a high damage to equipment.